Actually, the academy sits at about 7,300 feet. That's in the cadet area. The football stadium is quite a drop down at 6,600 feet. I only bring it up, not to quibble over the actual elevation, but to show that there's actually quite a large variance at the academy. The air force academy is the 2nd largest college campus in the united states with 18,000 acres. And because it sits on the side of the Rocky Mountains; "Literally", the elevation change is drastic. While the cadet area is 7,300 feet, there's still a lot more of the campus that goes higher than that. The lowest point at the academy is right at the south gate. It's approximately 6,200 feet. The highest point at the academy is at the recreation area. It tops 9,000 feet.
With all that said, your body will get use to the altitude. You don't need any fancy contraptions that will only waste your money. Your first couple weeks at the academy is in the cadet area. Normal Physical fitness, military bearing, etc. The academy keeps a close eye on you. By the time the 2nd half of BCT starts and you get involved more physically, you'll be getting accustomed to the area. Don't sweat it.